54 Dr. T. Godlewski on some 



Table III. 



T (in minutes). Activity. 



3 900 



4 890 



5 910 



6 900 



At this period the crystallization started. 



8 1000 



10 1180 



12 1250 



14 1350 



17 . 1530 



22 1710 



27 1780 



At this period the crystallization ended. 



30 1780 



35 1780 



On the surface of the plate some drops of distilled water 

 were now added, and the dish was placed again on the 

 water-bath, so that the crj^stals melted in the water of 

 crystallization. The measurements were repeated in the 

 same manner as before. 



In the moment when the second crystallization started, 

 the activity of the solution was 1530 ; when it was finished 

 the activity of the plate was 2830. 



After the third crystallization the activity was 2910. 



The fourth and fifth and sixth crystallizations did not 

 cause a further increase of the activity. 



This maximum activity then decayed with the time and 

 reached the value 935 after three days, and, disregarding 

 small irregular oscillations, remained constant at this value 

 through many weeks. 



Similar experiments were repeatedly made, and gave the 

 same qualitative results. 



These experiments show that the /3 activity of uranium 

 nitrate is very considerably augmented by the actual process 

 of crystallization , and it will be proved later that the decay 

 of activity noted immediately after crystallization is due to 

 the loss of this excess of activity produced by crystallization. 



The explanation of the increase of activity at the moment 

 of crystallization is very simple. We know that all the /? 

 activity of uranium proceeds not from the uranium itself, but 

 from UrX. But UrX is so readily soluble in water that it 

 is possible, as we have seen, to separate UrX from uranium 

 by fractional crystallization. If, as usually the case, the hot 



